1. Field of the invention
This invention relates to a process and apparatus for the continuous preparation of striped or marbled detergent bars. The invention is particularly directed to coloured liquid injection into a soap mass so that a multicoloured striped, marbled or mottled bar is the end product.
2. The prior art
Processes are already known according to which soaps with coloured stripes can be prepared. It has been suggested, for example, that coloured soap can be prepared by bringing different coloured soap rods together and compressing them. Tablets of soap made in this way contain sharply defined stripes, but it is not possible to produce soaps with very fine striations according to this process. It was also found that the use of an additional mixing device, which is required by this process, makes the capacity of the plant much smaller than that of a normal soap plodder.
Processes are also known for the preparation of striped soap by incorporating in the soap mass solutions or dispersions of dyes in the conveyor or vacuum section of the plodder. The striped effects achieved in this way are not satisfactory, because uncontrollable mixing, particularly in the worm section of the plodder, causes the stripes to be smeared or to disappear. Because the mixing is more vigorous inside the soap rod than at the edges, soap tablets prepared in this way have a satisfactory striped pattern on the surface of the tablet, but the stripes disappear in the middle, and so such tablets rapidly become plain in use.